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Abstract:

A ion source for a mass spectrometer comprises: a capillary having a
nozzle for emitting a nebulized fluid sample; an electrode of the
capillary; a high voltage power supply; a second electrode disposed
within or configurable to be disposed within a path of the nebulized
fluid sample; and at least one switch for selecting application of an
electrical potential provided by the high voltage power supply to either
or both of the capillary electrode or the second electrode, wherein the
capillary and capillary electrode are configurable so as to ionize the
nebulized fluid sample by electrospray ionization and the second
electrode is configurable so as to ionize the nebulized sample by
atmospheric pressure chemical ionization.

Claims:

1. A ion source for a mass spectrometer comprising: a capillary having a
nozzle for emitting a nebulized fluid sample; an electrode of the
capillary; a high voltage power supply; a second electrode disposed
within or configurable to be disposed within a path of the nebulized
fluid sample; and at least one switch for selecting application of an
electrical potential provided by the high voltage power supply to either
or both of the capillary electrode or the second electrode, wherein the
capillary and capillary electrode are configurable so as to ionize the
nebulized fluid sample by electrospray ionization and the second
electrode is configurable so as to ionize the nebulized sample by
atmospheric pressure chemical ionization.

2. An ion source as recited in claim 1, wherein the second electrode is
moveable between positions wherein the second electrode is and is not
disposed within the path of the nebulized fluid sample, respectively.

3. An ion source as recited in claim 2, further comprising a rotatable
holder for the second electrode, a rotation of the rotatable holder
effecting the movement of the second electrode between positions wherein
the second electrode is and is not disposed within the path of the
nebulized fluid sample, respectively.

4. An ion source as recited in claim 3, further comprising a ground
contact that is in electrical communication with the second electrode
when the second electrode is not disposed within the path of the
nebulized fluid sample.

5. An ion source as recited in claim 1, further comprising a heater in
thermal contact with the capillary.

6. An ion source as recited in claim 1, wherein the capillary tip is
disposed at a distance from an ion inlet aperture of the mass
spectrometer that is intermediate between optimal distances from the ion
inlet aperture associated with electrospray-only and
atmospheric-pressure-chemical-ionization-only operation.

7. A system for ionizing samples for input to a mass spectrometer,
comprising: a housing comprising: an aperture; a first electrical
contact, said first electrical contact configurable to be in electrical
communication with a high voltage power supply; and a second electrical
contact, said second electrical contact in electrical communication with
a corona discharge electrode disposed proximal to an ion inlet aperture
of the mass spectrometer; a first assembly matable with the housing,
comprising: a capillary having a nozzle for emitting a nebulized fluid
sample, the capillary disposed within the aperture of the housing when
the first assembly is mated to the housing; an electrode of the
capillary; and an electrical contact in electrical communication with the
electrode, the electrical contact in electrical communication with the
first electrical contact of the housing when the first assembly is mated
to the housing; and a second assembly matable with the housing,
comprising: a capillary having a nozzle for emitting a nebulized fluid
sample, the capillary disposed within the aperture of the housing when
the first assembly is mated to the housing; a first electrical contact in
electrical communication with the first electrical contact of the housing
when the second assembly is mated to the housing; and a second electrical
contact in electrical communication with the second electrical contact of
the housing when the second assembly is mated to the housing, wherein the
first and second assemblies are interchangeably matable with the housing
for ionizing the sample by electrospray ionization (ESI) and atmospheric
pressure chemical ionization (APCI) respectively.

8. A system as recited in claim 7, further comprising: a channel of the
housing supplying a nebulizing gas; at least one channel of the first
assembly for receiving the nebulizing gas when the first assembly is
mated to the housing and for delivering the nebulizing gas to a vicinity
of a tip of the capillary of the first assembly; and at least one channel
of the second assembly for receiving the nebulizing gas when the second
assembly is mated to the housing and for delivering the nebulizing gas to
a vicinity of a tip of the capillary of the second assembly.

9. A system as recited in claim 7, further comprising: a heater of the
housing for heating the nebulized fluid sample emitted by either the
capillary of the first assembly or the capillary of the second assembly.

[0002] The present invention generally relates to mass spectrometry and,
more particularly, to ion sources for generating ions from a sample and
delivering the ions to a mass spectrometer.

BACKGROUND OF THE INVENTION

[0003] Mass spectrometry is a well-established method of analyzing for the
presence and concentration (or amount) of a wide variety of chemical
constituents with high sensitivity. Since mass spectrometric analysis
includes detection or quantification of various ions having varying
mass-to-charge ratios, it is necessary to ionize the molecules of
chemical constituents of samples of interest. Heated electrospray
ionization (HESI) and atmospheric pressure chemical ionization (APCI) are
two common ionization techniques that may be employed to ionize chemical
constituents of samples provided in liquid form. These two techniques are
somewhat similar in the sense that both require nebulization of a liquid
sample spray within a flow of heated gas. However, some fundamental
differences exist between the two techniques. The HESI source sprays a
nebulized liquid spray where the tip of the sprayer (e.g., a nozzle such
as of a capillary tube) has or provides an electrical potential that
transfers charge to the droplets. These droplets are then dried by a
heated flow of gas before being injected into the mass spectrometer.
Although the APCI source also emits a spray of nebulized liquid, the tip
of the sprayer does not carry an electrical charge and, in fact, is often
grounded. The neutral droplets so produced are dried by a heated flow of
gas and then are ionized by way of a corona discharge needle placed
between the sprayer and the mass spectrometer.

[0004] A HESI sprayer is long enough so that the tip sits outside of the
heater region so that the drying gas is heated but the liquid flow is not
directly heated. Conversely, an APCI sprayer is shorter so that it sits
within the heater region so that the liquid droplet flow is directly
heated.

[0005] The two above-described ionization techniques are, to some extent,
complementary because certain classes of compounds that ionize well in
HESI (or ESI) mode often do not ionize well in APCI mode, and vice versa.
In some high throughput screening applications, where the amount of
sample available is limited and where time is critical, it is desirable
to limit the amount of time required in order to identify all the
components in the sample. Therefore, it is desirable to be able to switch
between the two aforementioned ionization modes with a minimum of time
and inconvenience.

SUMMARY

[0006] To address the need for easy and convenient changeover or switching
between ESI (or HESI) and APCI ion sources, two related approaches are
disclosed herein. Accordingly, in a first aspect of the present
teachings, a switchable ion source is provided that can operate in either
an HESI-only mode, an APCI-only mode or a "combined mode". The apparatus
facilitates easy and rapid selection between HESI (or ESI) and APCI
ionization techniques and, in the combined mode, enables two types of
ionization mechanisms to be performed simultaneously to ionize a single
sample. Accordingly, a combination HESI/APCI source is described so that
either HESI or APCI can be achieved using the same source housing. This
is achieved by producing a sprayer having a length intermediate between
the lengths of conventional HESI-only and APCI-only sprayers.
Furthermore, when HESI mode is in use, the sprayer tip receives an
electrical potential and the corona discharge needle is grounded. When
APCI mode is in use, the sprayer tip is grounded (or given a small
electrical potential) and the corona discharge needle is supplied an
electrical potential. Software may be employed to switch between HESI and
APCI operational modes between analyses employing different analysis
protocols. A single power supply is provided so as to provide operating
voltage to either an HESI sprayer, to an APCI needle electrode or to both
the sprayer and the APCI needle. The APCI needle may be provided on a
moveable or rotatable support that may permit the APCI needle to
physically move, under software control, between two positions: a first
position--used when Atmospheric Pressure Chemical Ionization is in
effect--between the nozzle and an ion inlet aperture of a mass
spectrometer and a second position--used when APCI is not in effect--that
is removed from the region between the nozzle or sprayer and the ion
inlet aperture.

[0007] In a second aspect of the present teachings, modular
interchangeable HESI (or ESI) and APCI nozzle assemblies are disclosed,
either of which may be mated to a common housing which provides all
necessary gas and electrical connections to the mated nozzle assembly.
The HESI nozzle assembly includes a single electrical contact that, in
operation, mates with an electrically live electrical contact of the
housing. Since the single electrical contact of the HESI probe is in
electrical communication with the HESI nozzle or sprayer, an operating
voltage may thus be applied to the HESI nozzle or sprayer. The APCI
nozzle assembly includes a first electrical contact that, in operation,
mates with the same electrically live electrical contact of the housing.
The APCI nozzle assembly further includes a second electrical contact
that, in operation, mates with a second electrical contact of the
housing. The first and second electrical contacts of the APCI nozzle
assembly are in electrical communication with one another. However, these
two electrical contacts may not be in electrical communication with the
nozzle or sprayer portion. Thus, in operation, the APCI nozzle assembly
may provide a simple electrical bridge between the two electrical
contacts of the housing. Since the second housing electrical contact is
in electrical communication with an APCI needle within the housing,
operating voltage may thus be provided to the APCI needle when the APCI
housing assembly is in its operating position.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The above noted and various other aspects of the present invention
will become apparent from the following description which is given by way
of example only and with reference to the accompanying drawings, not
drawn to scale, in which:

[0009]FIG. 1 is a schematic illustration of a combination ion source in
accordance with the present teachings operated in a configuration so as
to generate ions only by electrospray (ESI) or heated electrospray (HESI)
ionization;

[0010]FIG. 2 is a schematic illustration of the combination ion source of
FIG. 1 operated in a first alternative configuration so as to generate
ions only by Atmospheric Pressure Chemical Ionization (APCI);

[0011]FIG. 3 is a schematic illustration of the combination ion source of
FIG. 1 operated in a second alternative configuration so as to generate
ions simultaneously by ESI (or HESI) and by APCI;

[0012]FIG. 4 is a schematic illustration of another combination ion
source in accordance with the present teachings operated so as to
generate ions only by ESI or HESI ionization;

[0013]FIG. 5 is a perspective illustration of an HESI source probe and a
perspective illustration of a separate APCI probe, the HESI and APCI
source probes being interchangeable within a single housing in accordance
with another aspect of the present teachings;

[0014]FIG. 6 is a perspective view of a receptacle of a housing for the
HESI and APCI source probes of FIG. 5; and

[0015] FIG. 7 is a schematic cross-sectional view of a an ionization
chamber and common housing for the HESI and APCI nozzle assemblies of
FIG. 5.

DETAILED DESCRIPTION

[0016] The following description is presented to enable any person skilled
in the art to make and use the invention, and is provided in the context
of a particular application and its requirements. Various modifications
to the described embodiments will be readily apparent to those skilled in
the art and the generic principles herein may be applied to other
embodiments. Thus, the present invention is not intended to be limited to
the embodiments and examples shown but is to be accorded the widest
possible scope in accordance with the features and principles shown and
described. To appreciate the features of the present invention in greater
detail, please refer to FIGS. 1-7 in conjunction with the following
discussion.

[0017] The terms "mass spectrometry" or "MS" as used herein refer to
methods of filtering, detecting, and measuring ions based on their
mass-to-charge ratio, m/z, sometimes given in units "Da/e" (Daltons per
elemental charge unit). In general, one or more molecules of interest are
ionized and the ions are subsequently introduced into a mass spectrometer
instrument where, due to a combination of magnetic or electric fields,
the ions follow a path in space that is dependent upon mass ("m" or "Da")
and charge ("z" or "e").

[0018] After the sample has been ionized, the positively charged or
negatively charged ions thereby created may be analyzed to determine a
mass-to-charge ratio (i.e., Da/e). Suitable analyzers for determining
mass-to-charge ratios include quadrupole analyzers, ion trap analyzers,
time-of-flight analyzers, electrostatic trap analyzers as well as others.
The ions may be detected by using several detection modes. For example,
selected ions may be detected (i.e., using a selective ion monitoring
mode (SIM)), or alternatively, ions may be detected using selected
reaction monitoring (SRM) or multiple reaction monitoring (MRM). Ions can
also be detected by scanning a mass spectrometer to detect all the
precursor ions simultaneously or all the products ions of a specific
precursor ion simultaneously or both.

[0019] FIGS. 1-3 illustrate various embodiments of an ionization apparatus
100 in accordance with the present teachings utilized in three different
modes of operation. The apparatus 100 comprises a capillary 108 that
receives a sample stream from, for instance, a liquid chromatograph
column and that nebulizes the sample, possibly with pneumatic assistance
from a sheath gas delivered by means of a gas channel (not shown)
surrounding or adjacent to the capillary. The capillary 108 or the
flowing sample in the capillary may be maintained at a high voltage
provided by a high-voltage power supply 101 that is electrically coupled
to the capillary or to the sample by a series of electrical lines
including switches 102a-102c. The capillary may thus be used as an
electrospray ion source under the influence of an electric field
developed as a result of a voltage difference between the capillary or
the sample and a counter electrode. Accordingly, the capillary 108 may
also be referred to as an HESI needle (or, simply, as a "nozzle") in this
document. In operation, a spray 111 of droplets and possibly free ions is
emitted from an end of the capillary 108 in the direction of an ion inlet
aperture 110 of a vacuum chamber of a mass spectrometer. Nebulization of
the sample and evaporation of solvent may be assisted by a heater 109 in
thermal contact with the capillary.

[0020] The novel apparatus 100 further comprises an APCI corona discharge
electrode (e.g., a needle) 106 that may be fitted to a moveable support
structure 104, such as a rotating stage (as illustrated). The moveable
support structure 104 is operable so as to either position a tip of the
needle 106 outside of the spray 111 (in a first position as shown in FIG.
1), or alternatively, to position the needle tip within the spray 111 (in
a second position as shown in FIG. 2). The movement of the APCI needle
106 (or equivalently, of the moveable support 104) between these first
and second positions may cause an electrical contact that is coupled to
the APCI needle to either come into contact with ground potential so as
to maintain the needle 106 at ground potential or to come into contact
with an electrical line that may be placed in electrical continuity with
the high-voltage supply 101. Concurrently with the movement of the APCI
needle 106 between these first and second positions, the electrical
switches 102a-102c are reconfigured so as to provide voltage from the
high voltage source 101 to either the HESI needle 108 or to the APCI
needle 106 (or both), thereby allowing easy changeover between HESI, APCI
and combined ionization modes.

[0021] In either the HESI (FIG. 1) or APCI (FIG. 2) mode of operation, an
analyte-bearing liquid, comprising the analyte dissolved in a suitable
solvent, is caused to flow through the capillary 108. The liquid is
caused to be nebulized and ejected from the capillary, at least in part,
by an inert sheath gas (not shown) which flows around an outlet aperture
of the capillary. The formation or liberation of ions from the resulting
droplets varies, as described below, depending on which ionization mode
is employed. The ions are then input to a vacuum chamber of a mass
spectrometer (not shown) for mass analysis through an ion inlet aperture
110.

[0022] In the HESI mode of operation, shown below in FIG. 1, charged
liquid droplets are emitted from the capillary outlet aperture under
exposure of the liquid in the capillary to a high voltage, taken with
reference to the voltage of a counter electrode. The electrode may
comprise a wire passing through the bore of the capillary or may comprise
a conductive coating on the capillary tip. Alternatively, the capillary
may be fabricated from a conductive material so as to, itself, be the
electrode. The ion inlet aperture of a mass spectrometer may function as
the counter electrode, or a separate electrode between the capillary and
the MS ion inlet aperture may fulfill this function. The high voltage
difference may be achieved by applying high voltage, supplied from HV
power supply 101, to the capillary electrode and maintaining the counter
electrode at ground potential. With a proper application of voltage and
flow, a Taylor cone is formed at the capillary outlet aperture which
breaks up into a plume (spray) of emitted charged droplets. De-solvation
and solvent evaporation causes analyte ions to be liberated from these
droplets.

[0023] As mentioned above, the novel ion source apparatus also includes a
corona discharge electrode (e.g., an APCI needle) 106 which may be moved
into or out of the path between an outlet aperture of the capillary 108
(a capillary tip) and the MS ion inlet aperture 110. As shown in the
present diagrams, the corona discharge electrode may be supported by a
rotatable stage which can rotate through an angle. In the HESI-only (or
ESI-only) mode of operation (FIG. 1), the rotatable stage is positioned
such that the corona discharge electrode is rotated to a position where
its presence has no effect, electrostatic or otherwise, on performance.
In this position, it is also not subject to contamination by the spray.
However, in an APCI-only mode of operation, shown in FIG. 2, the needle
is rotated to a position normal for APCI mode--that is, between the tip
of the capillary 108 and the MS ion inlet aperture 110. Although the
corona discharge electrode is shown, in the accompanying figures, as
being attached to a rotating stage, it is to be kept in mind that the
positioning and re-positioning of this electrode may be facilitated with
the aid of any other type of moveable support, such as a translation
stage. The position of the moveable support and electrode may be changed
with a manual control accessible from the outside of the ion source
housing or, alternatively, with a stepper motor. When employed, such a
stepper motor may be controlled by a computer or other electronic
controller module (not shown) for automatic switching.

[0024] As may be observed by inspection of FIG. 2, during operation in
APCI-only mode, the capillary electrode is grounded (or maintained at a
relatively low electrical potential) and the high voltage from the supply
HV is routed to the corona discharge needle so as to cause development of
a corona discharge 107 within the path of the spray 111. The corona
discharge generally represents ionized solvent vapor. This ionized
solvent vapor then acts as a chemical ionization reagent so as to form
the desired analyte ions by reaction. This configuration is in contrast
to the configuration used for operation in HESI-only (or ESI-only) mode
(see FIG. 1), in which high voltage is supplied to the capillary
electrode and the corona discharge electrode is not energized or is
grounded. When operation is in the HESI-only mode, the corona discharge
electrode could alternatively be connected to another intermediate
voltage (not shown) so as to further minimize any electrostatic effect on
fields within the source housing and speed up switching. The voltage
routing may be accomplished with the aid of one or more switches, as
shown in schematic fashion in the accompanying figures. The switches may
be mechanical or electronic and may be operated manually or automatically
under the control of a computer or other electronic controller module
(not shown).

[0025] As illustrated in FIG. 3, the apparatus 100 allows for a combined
mode of operation, in which the APCI needle is in the APCI position, and
both the electrode associated with the HESI capillary and the corona
discharge electrode (APCI needle) are energized. This mode resembles
HESI, with high voltage applied the capillary tip, but also includes
APCI, with high voltage routed to the corona discharge electrode. In this
combined mode of operation, the APCI needle and HESI sprayer operate in
tandem, thus possibly producing a wider variety of ions than would be
generated by using either one of the HESI or APCI techniques alone.

[0026]FIG. 4 is a schematic illustration of an alternative ion source 150
in accordance with the present teachings. The ion source 150 is similar
to the source 100 (FIGS. 1-3) except that the APCI needle 106 is not
moveable and remains fixed in position even when the apparatus is
operated in electrospray mode, without APCI ionization. An additional
switch or switches, such as switch 102d may be employed operated so as to
connect the APCI needle 106 to ground or to some other potential when
APCI mode is not in operation. FIG. 4 only shows an operating mode or
configuration in which ions are only generated by the HESI (or HESI)
process and, thus, is analogous to FIG. 1. However, APCI-only and
combined ionization modes are also possible.

[0027]FIG. 5 illustrates perspective views of an HESI nozzle assembly 200
and an APCI nozzle assembly 210, in accordance with another aspect of the
present teachings. The HESI and APCI source nozzle assemblies shown in
FIG. 5 are modular and interchangeable in the sense that can both be
mated to a single housing that provides all necessary electrical and gas
connections to either nozzle assembly. The housing also provides the
heater for the nozzle and the APCI needle. In order to reconfigure a mass
spectrometer so as to use one or the other of the ionization techniques,
a user manually removes one of the source nozzle assemblies and replaces
it with the other assembly. All electrical and gas connections are hidden
within the housing and, thus, such removal and replacement is a simple
and fast procedure.

[0028] As is illustrated in FIG. 5, the nozzle 204 of the assembly 200
employed for electrospray ionization has a length L1 which is
greater than the length L2 of the nozzle 206 of the assembly 210
employed for APCI ionization. These different lengths are in accordance
with the different optimal nozzle-to-aperture distances for these two
ionization modes, as determined by experiment. The nozzle-to-aperture
distance is analogous to the distance between the emitting tip of
capillary (or nozzle) 108 and the ion inlet aperture 110 in FIGS. 1-4.

[0029] The separate nozzle-to-aperture distances for the modular
interchangeable HESI and APCI nozzle assemblies (FIG. 5) are to be
distinguished from the single nozzle-to-aperture distance for the
embodiments illustrated in FIGS. 1-4. In both the combination ion source
100 (FIGS. 1-3) and the combination ion source 150 (FIG. 4), the single
nozzle-to-aperture distance is configured intermediate between the
respective optimal nozzle-to-aperture distances corresponding to HESI and
APCI operation. In this fashion, the ionization performance of the
combination ion sources 100, 150 is adequate for each of the modes of
operation without requiring mechanical adjustment of the nozzle.

[0030] The HESI nozzle assembly 200 (FIG. 5) comprises a single electrical
contact 202a which mates with an electrical contact of the housing
(described following). The APCI nozzle assembly 210 (FIG. 5) also
incorporates the electrical contact 202a as well as a second electrical
contact 202b that mates with a second electrical contact of the housing.
The electrical contact 202a of the HESI nozzle assembly 200 is in
electrical communication with an electrode of the nozzle 204 and, thus,
in operation, may provide a high voltage to the electrode of the nozzle
204. In contrast, the electrical contact 202a of the APCI nozzle assembly
210 is in electrical communication with the second electrical contact
202b but may not be in electrical communication with an electrode of the
nozzle 206.

[0031]FIG. 6 is a perspective view of a receptacle portion of a housing
for the HESI and APCI source probes of FIG. 5. The housing 250 comprises
a flat plate portion 251 which, in operation, comes into sealing contact
(perhaps by means of an intermediate gasket or O-ring) against a mating
flat plate portion 212 of either of the HESI and APCI nozzle assemblies
200, 210 shown in FIG. 5. A channel 254 within the housing admits and
provides a passageway for either of the nozzles 204, 206 when the
respective nozzle assembly is in operational position. At least one
recessed area surrounding the channel 254 comprises slots or grooves 256a
and 256b. A respective electrical contact of the housing is disposed
within each such slot or groove. Thus, first electrical contact 252a is
disposed within the recessed area within slot or groove 256a and second
electrical contact 252b is disposed within the recessed area within slot
or groove 256b. The first electrical contact 252a is in electrical
communication with an electrical power supply apparatus and thus is
maintained at a live high voltage. The second electrical contact 252b is
in electrical communication with an APCI needle that is disposed within
the housing. The APCI needle is energized only when voltage is supplied
to the second electrical contact 252b.

[0032] The electrical contacts of the housing are designed to mate with
respective electrical contacts of the nozzle assemblies. Thus, the
electrical contact 252a, which has a live voltage provided from a power
supply, mates with the electrical contact 202a of either the HESI nozzle
assembly 200 or the APCI nozzle assembly 210. When the HESI nozzle
assembly 200 is in operating position in contact with the housing, high
voltage is supplied to an electrode of the nozzle 204 via the contact
between electrical contact 202a and electrical contact 252a. Since the
HESI nozzle assembly 200 does not have a mating electrical contact to
mate with the second housing electrical contact 252b, the APCI needle is
not energized when the HESI nozzle assembly is installed. However, when
the APCI nozzle assembly 210 is in operating position in contact with the
housing, electrical continuity is established between the two electrical
contacts 252a and 252b that are within the housing, since the APCI nozzle
assembly 210 provides an electrical bridge. Thus, when the APCI nozzle
assembly 210 is in operating position, high voltage is supplied to the
APCI needle within the housing. In some embodiments, the electrical
contact 202a of the APCI nozzle assembly 210 may not be in electrical
contact with an electrode of the nozzle 206 or, in fact, the nozzle 206
may not even have an electrode associated with it. However, in other
embodiments an electrode may be provided as part of the nozzle 206 and
said electrode may be in electrical communication with the electrical
contact 202a. In such embodiments, both an electrode of the nozzle as
well as an APCI needle may be energized simultaneously, so that ions are
produced by both of the electrospray and atmospheric chemical ionization
processes. In such embodiments, the nozzle length L2 may be longer
that as shown in FIG. 5 so as to provide adequate ionization by both
processes simultaneously.

[0033] Novel ion sources for mass spectrometry have been disclosed. The
above-described apparatus allows switching between HESI (or ESI) only,
APCI only and combined mode with a minimum of inconvenience, and, in
various embodiments, with no compromise of performance when in HESI only
or APCI only modes. The HESI, APCI, and combined sprayers can consist of
easy to change sprayer inserts. As an additional advantage, the
embodiments shown in FIGS. 1-4 do not require manual intervention by a
user in order to switch between ionization modes. Thus, the embodiments
illustrated and discussed herein, or variants thereof, may be utilized in
clinical mass analyzers (which may provide limited opportunities for
manual user intervention) such as, for example, the mass analyzers
described in a co-pending U.S. Provisional Application for patent, Appl.
No. 61/408,180 titled "Automated System for Sample Preparation and
Analysis" (Attorney Docket No. TFS-13) filed on Oct. 29, 2010 and
incorporated by reference herein as if fully set forth herein.

[0034] FIG. 7 is a schematic cross-sectional view of the common housing
250 for the HESI and APCI nozzle assemblies of FIG. 5, mounted onto an
ionization chamber 261. The second electrical contact 252b, which makes
contact with a pin of the APCI nozzle assembly 210, is electrically
connected to the APCI needle electrode 106 by means of an electrical
conductor 259 such as a wire. Although the electrical conductor 259 is
shown disposed externally to the housing 250 and ionization chamber 261
in FIG. 7, it may be alternatively mounted in any fashion, such as
disposed within the housing 250 or ionization chamber 261 or within one
or more channels within or attached to these components. A first gas
inlet port 253 provides a nebulizing gas which, in operation, is
introduced into a mating inlet hole in either the HESI nozzle assembly
200 or the APCI nozzle assembly 210. The nebulizing gas is carried
through a dedicated channel or passageway in either of the nozzle 204 or
the nozzle 206 to the nozzle tip where it assists in producing a fine
spray of droplets from a sample. A second gas inlet port 255 is used to
introduce an auxiliary gas which assists in desolvation of the sample
droplets. The auxiliary gas is prevented from escaping the housing to
atmosphere by O-ring 265. The housing 250 includes a common heater 109
which, in operation, is used to heat the auxiliary gas and droplets after
they exit either the HESI or APCI nozzle tip in order to facilitate
desolvation. The heater 109 is supported by a heater support 258 and is
mounted in contact with a thermocouple 257 that is employed, in
operation, for temperature measurement and control. The movable support
104 for the APCI needle 106 may be operated by a motor or may, as
illustrated in FIG. 7 be mounted to a wall of the ionization chamber 261
so as to be manually operable by a user.

[0035] The discussion included in this application is intended to serve as
a basic description. Although the present invention has been described in
accordance with the various embodiments shown and described, one of
ordinary skill in the art will readily recognize that there could be
variations to the embodiments and those variations would be within the
spirit and scope of the present invention. The reader should be aware
that the specific discussion may not explicitly describe all embodiments
possible; many alternatives are implicit. Accordingly, many modifications
may be made by one of ordinary skill in the art without departing from
the spirit, scope and essence of the invention. Neither the description
nor the terminology is intended to limit the scope of the invention. All
patent application disclosures, patent application publications or other
publications are hereby explicitly incorporated by reference herein as if
fully set forth herein.